Why are we debating this? It is called density dependent birth rates due to urbanization and the increasing education and employment of women during prime child bearing years.

When young women have to work because the urbanization requires a larger nest egg then women naturally put off children.

Vico, Spengler, Glubb, Unwin aka the anti-whig cyclic historians all talked about how this simply the natural fate of civilization and John C Calhoun's utopia mouse experiment give us evidence that this could be considered extension of law of competitive exclusion applied to social mammals i.e. at certain point niche competition becomes to high when population density increases and so people drop out of the rat race so to speak.

You should talk about how briefly Hilter reversed the situation with a Keyesian program of state spending aka massive loans to married men which were reduced by 25% per child.

I think it possible to use State power to structure incentives to promote fertility just as it possible for the use of protectionism to promote industry.

I keep saying that the modern sexual revolution was not born in the 1960s, nor were the politics that grew out of it. They were born in the late-19th and early-20th century. This is well-known by social historians (but it disrupts the 'postmodernism is to blame' narrative).

Birth control was used, promoted and highly popular in the late-19th and early-20th century. Birth rates started to fall because of this. But is was never dramatic. The birth rate still would have remained above the replacement rate, I think.

The key to understanding the major dip in the data in the 1920s and 1930s is to understand (a) the major population and cultural changes brought on by WWI and (b) the economic turmoil of the era. The period 1914-1939 was a major period of decadence and degeneration for Western civilisation. It very nearly never recovered.

It did recover, however. But briefly. After World War II there was a burst of optimism and a reestablishment of pro-social sentiments. This was the era of the baby boom. Birth rates reached acceptable levels of equilibrium growth. Not as high as in the mid-19th century - those were certainly too high! - but healthy enough to generate expansion.

Then came the 1960s and the second wave of the sexual/cultural revolution. The post-war optimism floundered and society entered its second phase of terminal moral degeneration. We live at the tail-end of the second phase today and, so far as I can see, things are getting worse by the day.

Corruption is rampant and institutionalised. There is no leadership to speak of. The economy has collapsed into a stagnant kleptocracy. Younger people have no capacity for moral judgement and confuse aggressive posturing against invented enemies for virtue; when it is precisely the opposite.

I am not optimistic. It seems to me now a situation that requires damage control.

No. Christianity and religion began to decline in the West in the late-19th century mainly by reversion to scientistic and materialist worldviews such as those of Darwin, Marx and Freud.

By the 1910s, when the birth rate was really tanking, atheism itself started getting popular by the likes of Bertrand Russell.

All of this was accompanied by a slackening of moral norms. You can read this everywhere. In Keynes and the other Bloomsbury members; in the lifestyles of poets and authors like Oscar Wilde. You can even see it in the art of the era. Peter Hitchens thinks that the final nail in the coffin of a weak Christianity came in WWI. I think his argument is strong.

You appear to have a thoroughly mythic view of Western cultural and religious history. One that every non-informed person seems to hold.

Claim I: People were very Christian.Claim II: People were using birth control to decrease birth rates.

But the Church was against birth control. Yet people were using birth control. Obviously people were thus going against the Church.

How curious. *Wink*

This was the first phase of the collapse of Christianity. The Victorian sexual revolution undermined Church teachings on what sexual activity was all about (reproduction) and replaced them with materialist teachings (pleasure).

The next phase of the decline in Christianity came as divorce laws were weakened in the late-1960s. This led to divorce skyrocketing:

At this point the Church had lost all serious influence. It no longer influenced how people thought about sexuality. Nor did it influence how they thought about sexual relationships.

That is the history. Judge it how you will. I'm sure you'll insist that the secular, social democratic state can 'incentivise' people to reproduce and to treat the institution of marriage with respect. Maybe you'll even appeal to a utility function ;-). But that's obvious nonsense. It will never work.

Either morality changes or it doesn't. My bet is that it won't. And so the West will sink and other civilisations will take over.

(1) and yet the elite, the law and popular culture was strongly opposed to birth control in the late 19th century, e.g,

"A decade later (1876), Bradlaugh and Besant decided to republish the American Charles Knowlton's pamphlet advocating birth control, The Fruits of Philosophy, or the Private Companion of Young Married People, whose previous British publisher had already been successfully prosecuted for obscenity. The two activists were both tried in 1877, and Charles Darwin refused to give evidence in their defence, pleading ill-health, but at the time writing to Bradlaugh that his testimony would have been of little use to them because he opposed birth control. They were sentenced to heavy fines and six months' imprisonment, but their conviction was overturned by the Court of Appeal on the basis that the prosecution had not set out the precise words which were alleged to be obscene in the indictment. "https://en.wikipedia.org/wiki/Charles_Bradlaugh

(2) nor can you blame, as some people do, those "evil" liberals or Darwinists, e.g, Darwin and 19th century liberals like him rejected contraception: see here.

Birth control was very popular in this era. This is widely known. It is also manifestly obvious. How do you account for the fall in the birth rate if not by use of contraception? Did people just stop having sex? Come on. Let's get real here.

To be absolutely frank: you need to completely reevaluate your knowledge of cultural history. It is not strong and you seem to me to be propounding popular myths and misconceptions (mainly centered around the 'moralistic Victorian' which has been torn apart in social history since at least the early 1980s).

The Establishment opposed it. But the culture of this era was anti-Establishment. Hence the fact that the Establishment was opposed to birth control but everyone was using it. Even given these meager facts it is not hard to piece this together.